Zenithstar 61 back focus
- Aperture
- 61 mm
- Focal length
- 360 mm at f/5.9
- Image circle
- 43 mm
- Rear thread
- M54
- Corrector
- William Optics FLAT 61R
Checked against the manufacturer’s documentation in September 2026.
Cameras
| Camera | Back focus | Spacers | Result |
|---|---|---|---|
| Ares-C Pro | 56.0 mm | 22.0 mm | Exact |
| Artemis-C Pro | 56.0 mm | 38.5 mm | Exact |
| Neptune-C II | 56.0 mm | 27.0 mm | Exact |
| Poseidon-C Pro | 56.0 mm | 38.5 mm | Exact |
| Saturn-C SQR | 56.0 mm | 27.0 mm | Exact |
| Uranus-C | 56.0 mm | 27.0 mm | Exact |
| QHY183C | 56.0 mm | 22.0 mm | Exact |
| QHY183M | 56.0 mm | 22.0 mm | Exact |
| QHY268C (SBFL - Jan 2023 onward) | 56.0 mm | 20.6 mm | Within tolerance |
| QHY268M (SBFL) | 56.0 mm | 20.6 mm | Within tolerance |
| QHY294M Pro | 56.0 mm | 22.0 mm | Exact |
| QHY533C | 56.0 mm | 22.5 mm | Exact |
| QHY533M | 56.0 mm | 42.0 mm | Exact |
| QHY600M (SBFL) | 56.0 mm | 20.6 mm | Within tolerance |
| ASI071MC Pro | 56.0 mm | 22.0 mm | Exact |
| ASI1600MM Pro | 56.0 mm | 33.0 mm | Exact |
| ASI183MC Pro | 56.0 mm | 33.0 mm | Exact |
| ASI183MM Pro | 56.0 mm | 33.0 mm | Exact |
| ASI2400MC Pro | 56.0 mm | 17.5 mm | Exact |
| ASI2600MC Duo | 56.0 mm | 17.5 mm | Exact |
| ASI2600MC Pro | 56.0 mm | 22.0 mm | Exact |
| ASI2600MM Duo | 56.0 mm | 17.5 mm | Exact |
| ASI2600MM Pro | 56.0 mm | 22.0 mm | Exact |
| ASI294MC Pro | 56.0 mm | 33.0 mm | Exact |
| ASI294MM Pro | 56.0 mm | 33.0 mm | Exact |
| ASI533MC Pro | 56.0 mm | 33.0 mm | Exact |
| ASI533MM Pro | 56.0 mm | 33.0 mm | Exact |
| ASI585MC Pro | 56.0 mm | 33.0 mm | Exact |
| ASI585MM Pro | 56.0 mm | 33.0 mm | Exact |
| ASI6200MC Pro | 56.0 mm | 17.5 mm | Exact |
| ASI6200MM Pro | 56.0 mm | 17.5 mm | Exact |